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70 lines
1.5 KiB
C++
70 lines
1.5 KiB
C++
#include <iostream>
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#include <algorithm>
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#include <string>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 5e5 + 5;
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const int mod = 114514;
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int n, sum[N][26], pre[26][26], suf[26][26], cnt[26];
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long long ans;
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std::string s;
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> s;
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n = s.size();
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s = ' ' + s;
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for (int i = 1; i <= n; i++) {
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std::copy_n(sum[i - 1], 26, sum[i]);
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sum[i][s[i] - 'a']++;
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}
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for (int i = n; i; i--) {
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cnt[s[i] - 'a']++;
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for (int j = 0; j < 26; j++) {
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if (s[i] - 'a' == j) continue;
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suf[s[i] - 'a'][j] = (suf[s[i] - 'a'][j] + cnt[j]) % mod;
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}
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}
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std::fill_n(cnt, 26, 0);
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for (int i = 1; i <= n; i++) {
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cnt[s[i] - 'a']++;
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for (int j = 0; j < 26; j++) {
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if (cnt[j] < 2 || s[i] - 'a' == j) continue;
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pre[s[i] - 'a'][j] = (pre[s[i] - 'a'][j] + (static_cast<long long>(cnt[j]) * (cnt[j] - 1) / 2) % mod) % mod;
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}
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for (int j = 0; j < 26; j++) {
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if (s[i] - 'a' == j) continue;
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suf[s[i] - 'a'][j] = (suf[s[i] - 'a'][j] - (sum[n][j] - sum[i - 1][j]) % mod + mod) % mod;
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}
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for (int j = 0; j < 26; j++) {
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for (int k = 0; k < 26; k++) {
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if (j == k || j == s[i] - 'a' || k == s[i] - 'a') continue;
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ans += static_cast<long long>(pre[k][j]) * suf[j][k];
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}
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}
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ans %= mod;
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}
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cout << ans << endl;
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return 0;
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}
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